The present invention relates to an image generation system, an image generation method, an information storage medium, and the like.
A known image generation system may be configured to generate an image viewed from a given viewpoint in an object space in which an object (e.g., moving object) is placed. Such an image generation system is very popular as a system that makes it possible to experience virtual reality. For example, when the image generation system is designed to implement a fighter aircraft game, the player enjoys the game by operating a player's fighter aircraft (that imitates a fighter aircraft) so as to fly in the object space and attack the attack target (e.g., enemy fighter aircraft or enemy's position).
It is desired for such an image generation system to render (display or implement) an image with higher quality. For example, it is desirable that such an image generation system be able to render (display or implement) a realistic image of clouds that are suspended in air. For example, JP-A-2009-53886 discloses a related-art image generation system that generates an image of clouds. According to the technology disclosed in JP-A-2009-53886, a plurality of billboard polygons (e.g., a billboard polygon for a distant view and a billboard polygon for a near view) are placed in the object space, and an image of clouds is drawn on each billboard polygon to generate a realistic image of clouds.
However, a known image generation system is configured so that clouds are merely displayed within the game screen in the form of an image. Specifically, a known image generation system is configured so that an assemblage of particles such as a cloud does not affect the attack capability, the defense capability, or the moving capability of a moving object (e.g., player's fighter aircraft or enemy fighter aircraft).